1. Field of the Invention
The present invention relates to an optical fiber connecting ferrule to be used in optical communication systems or optical measuring systems. Hereinafter it is referred to as "ferrule".
2. Description of Related Art
FIG. 5 shows a conventional ferrule 24 as comprising a cylindrical body 20 (2.5 mm across) of hard ceramics such as zirconia ceramics and a collared tubular catch 21 of a metal such as stainless steel. The cylindrical body 20 has a through aperture 23 of the same diameter as an optical fiber. In use, an optical fiber is inserted in the through aperture 23 of the cylindrical body 20 to be fixed thereto by an adhesive agent such as epoxy resin.
FIG. 8 shows a relay connector 22 having a ferrule 24 fitted therein. The relay connector 22 is jointed to a square plug 27 and to a round plug 28 via an associated adapter 26.
Specifically, the square plug 27 is press-inserted into one end of the relay connector 22 until it is locked by nails 22a. The other end of the relay connector 22 is attached to one hollow projection of the adapter 26 by rotating and threadedly engaging the tapped cap 22b of the relay connector 22 with the threaded hollow projection of the adapter 26. The round plug 28 is connected to the other hollow projection of the adapter 26 by rotating and threadedly engaging the tapped cap 28a of the round plug 28 with the threaded hollow projection of the adapter 26.
The relay connector 22 has a slotted sleeve 32 to put opposing optical fibers in linear alignment. The slotted sleeve 32 is of a metal such as copper (See FIGS. 7A and 7B).
As described above, the square plug 27 is connected to the round plug 28 in axial alignment, and their optical fibers are exactly aligned with the aid of the associated slotted sleeve
Assume that an external force is applied to the plug joint as indicated by arrow F in FIG. 8. Then, the ferrule body 24 cannot be flexibly deformed because it is of hard ceramics. The ferrules 27a and 28b of the square and round plugs 27 and 28 cannot be deformed, either. As a consequence, the slotted sleeve 32 will be expanded and deformed under stress.
As shown in FIG. 6, a conventional ferrule is used at the transmitting/receiving end of an optical communication apparatus 16, and application of undesired external force to the plug 25 will cause deformation of the slotted sleeve 32. Expansion of the slotted sleeve will cause an insertion loss in transmission at the relay connector, deteriorating the joint quality of opposing optical fibers.